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Discussion Starter · #1 ·
Slow, fast, short trips, whatever my truck is overheating. I started off with a quick look over and there was no thermostat installed. Will this fix the problem? There is also a crack around the radiator inlet on the drivers side and there is no overflow installed. The truck is a 1985 K5 Blazer with a 305. I have a 160* thermostat I am going to put in before work today. I might take it to work to see if it overheats again. Besides the cracked radiator there are no known leaks. The water pump indeed pumps and I noticed early on it was really low on coolant so I topped it off and have done my best to get all possible bubbles out. Any ideas?
 

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Yes a t-stat should help to add a restriction in the system. If there was nothing in there the water would be flowing too fast and not staying long enough to cool the block down before dumping back into the radiator.

What kind of fan do you have? If it is a mechinacal is it shrouded or electrical is it working properly?

How are your hoses? Does at least the lower one have a resistance so you cant squeeze it shut (internal spring)?
 

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Slow, fast, short trips, whatever my truck is overheating. I started off with a quick look over and there was no thermostat installed. Will this fix the problem? There is also a crack around the radiator inlet on the drivers side and there is no overflow installed. The truck is a 1985 K5 Blazer with a 305. I have a 160* thermostat I am going to put in before work today. I might take it to work to see if it overheats again. Besides the cracked radiator there are no known leaks. The water pump indeed pumps and I noticed early on it was really low on coolant so I topped it off and have done my best to get all possible bubbles out. Any ideas?
I think you've already identified a big part of the problem!
You have a crack in the radiatior inlet, and the coolant level was low, but say you have no known leaks? If you have a crack in the radiator, then it's not building pressure, which will cause it to over heat, and you're loosing coolant.
Since the PO removed the thermostat, he was trying to keep it from overheating, but probably made it worse. Get an overflow bottle installed as well.

That's why the cooling system is a closed system, radiator caps are rated for 7-13psi (over standard pressure). As you know from high school science class, when you increase the pressure, it raises the boiling point of the liquid. Since the radiator is leaking, it can't build the pressure, so the coolant boils over at 212* F rather than 240*F.

2 commom causes for over heating are:
Not enough air flow
Not enought coolant flow (bad water pump or a restriction/blockage)
 

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again, what kinda fan do you have, if its a stock clutch fan, replace it with a electric fan, you will notice i difference. and another thing, what kinda weather are you having where you live, big engines in our big trucks dont like alot of heat. but deffentaly fix or replace that radiator leak. and get yourself a overflow. pick in pull carry every thing you should need if not, auto zone has a new overflows that will bolt in to your engine bay. and as far as you not having a thermastate, thats fine. i never run one too. good luck
 

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ohhhh and one more thing, make sure your engine is running while filling up the radiator so you dont hydrolock your shit. bad bad bad bad bad
 

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Discussion Starter · #6 ·
I am running the stock clutch fan and shroud. I drove it to work tonight and though the truck did not over heat I stopped on the way home and checked out the radiator. It is also leaking from the top around the shroud. I was really trying to avoid a new radiator. Guess I'll have to bite the bullet on that one. There is an overflow in the vehicle but the radiator has no outlet for it. I'll ensure the new one does. I am also seeing some residual fluid around the water pump. I should probably replace that gasket while I am knee deep in antifreeze. I don't want to run an electric fan. No real reason. The weather here is terribly hot though.
 

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Your water pump has a weep hole, underneath, just behind the flange for the fan. If you have water leaking there, it's a bad pump. If I were you, I'd replace the radiator, pump, radiator cap (make sure it's intended to be used for a recovery bottle operation--not just a "generic" radiator cap). I'd also install a 190* thermostat; the 160* is too cool for a computer controlled engine.
 

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Not referring to fan control. The fuel injected engines are designed to operate at 195*+. The fuel/advance tables are programed to the higher temps. The engine will run rich at 165*.
 

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i had the same problem with my old radiator on my chevy, the over flow stem was broke. you can easly fix it if you want youself. just get a small brass tube, and soder it on. do not weld, sodder it good. you should also fill up your radiator again start it up and bring it to temp. see ifit is leaking from the water pump gasket or the wheep hole. you may just wanna break out capt. credidt card and replace it all........
 
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